Methane-induced lateral root formation requires the participation of nitric oxide signaling

Although methane (CH4)-induced lateral root (LR) formation has been discovered, the identification of downstream signaling compounds has yet to be fully elucidated. Here, we report a unique mechanism for the involvement of nitric oxide (NO) in the above CH4-mediated pathway in tomato (Solanum lycopersicum L.) and Arabidopsis thaliana. NO was produced rapidly in the root tissues of tomato seedlings when CH4 was administrated exogenously. The scavenging of NO with its scavengers prevented lateral root primordia formation and thereafter lateral rooting triggered by CH4. Gene expression analysis revealed that similar to the responses of sodium nitroprusside (SNP; a NO-releasing compound), CH4-induced SlCYCA2;1, SlCYCA3;1, and SlCDKA1 transcripts, and -downregulated SlKRP2 mRNA, were differentially abolished when endogenous NO was removed by its scavengers. Changes in the lateral root-related miRNA genes (SlmiR160 and SlmiR390a) and their target genes (SlARF16 and SlARF4), exhibited similar tendencies. Similar to those results in tomato, the addition of CH4 and SNP could obviously induce NO production and LR formation in Arabidopsis seedlings, which were correlated with the transcriptional profiles of representative LR-related genes. Combine with these findings in tomato and Arabidopsis thaliana, our results showed that NO might act, at least partially, as the downstream signaling molecule for CH4 control of lateral rooting.